Nice Rig thier Banjo, however, definitely change up that PSU and go straight to a Corsair HX 1kW for that set-up!!
Stick to a TRUE Push / Pull config...its proven.
Bear in mind, 4Ghz is not guarenteed.....
Having had a Raptor drive and change it out for a 640 Black in a heartbeat...noisy as hell and no noticeable gains...the only difference I see is how "quiet" the 640 Black is!